In existing long term evolution (LTE) systems, the same maximum number of hybrid automatic repeat request (HARQ) transmission are used by various services; i.e., when the number of HARQ transmission reaches the maximum number of HARQ transmission, retransmission is stopped. In an LTE system, parallel HARQ processes are used to perform radio link transmission; i.e., after transmission is completed in one process, it is unnecessary to wait for feedback for this process before a next process is used to transmit other data. In a frequency division duplex (FDD) mode, eight HARQ processes in total are used in the LTE system, and a transmission time slot corresponding to each process is one transmission time interval (TTI).
In the LTE system, a TTI bundling mode could be used by a user at an edge of a cell to perform the uplink transmission; i.e., same data is transmitted simultaneously in a plurality of continuous TTIs so that the transmission gain is increased. The plurality of TTIs for continuous transmission is referred to as a TTI bundle, and the amount of the TTIs for continuous transmission is referred to as a TTI bundle size. The same data transmitted simultaneously is actually a plurality of versions of a same data (i.e., a plurality of data blocks with different correction capabilities generated by a same data after being encoded). When the TTI bundling mode is used, TTIs in a same TTI bundle correspond to a same HARQ process for transmission, and four HARQ processes in total could be used in the existing LTE system.
During implementation of the present invention, the present inventor finds that when the mode used by a user equipment (UE) is switched from a normal mode (i.e., a non-TTI bundling mode) to a TTI bundling mode, the existing uplink transmission method is prone to causing errors in transmission, which decreases the transmission quality.